1. Field of the Invention
The invention relates to a system for supplying ink to an ink jet head, in particular an ink jet head that is composed of a plurality of modules in a stacked construction.
Such ink jet heads are used both in office printers and in small high-speed printers--the type needed for postage meters and product labeling devices--and, as a rule, have a relatively large number of jets.
Precisely in the latter application, a high degree of reliability is required, so that errors in printout, which can have major cost consequences, are avoided.
A component with especially major influence on the reliability of a printer is the ink jet head, along with its supply.
2. Description of the Related Art
An ink jet head composed of a plurality of modules is known from the prior art. See U.S. Pat. No. 4,703,333 to Hubbard. Each module has a number of jets and comprises a plurality of stacked plates with ink jet printing chambers and ink supply conduits machined into them. The module is a system of inclined and stacked arrays and it is constructed on the sideshooter principle. In other words, the jet conduits or openings extend crosswise through an outer plate. The pressure wave in the ink jet printing chamber extends in the direction of the jet conduit, so that the ink droplets are expelled orthogonally to the plate. Correspondingly, ink inlet conduits and openings for the ink supply are provided crosswise through the outer plate on the opposite of the module. To that end, one inlet neck is mounted on the plate above each ink inlet opening. The inlet necks, located in a line one after the other, of all the modules communicate with an ink tank via a common adapter with a following ink hose. The adapter is embodied as a fluid distributor element. Necks that are slipped onto the inlet necks of the modules are located on its ink outlet side. On its ink inlet side, there is a neck onto which the ink hose is slipped. The problem of pressure equilibrium for the ink inlet is still not addressed here.
Both for reasons of unhindered ink expulsion--via a side wall (side shooter)--and of the required space for the ink inlet, a scaled and offset system of the modules is necessary. This in turn requires a correspondingly large amount of space.
A multicolor ink jet printer is also known--see German patent disclosure DE 33 35 614 A1--in which fixed ink conduits lead from various ink tanks to the ink jet head. Because of this rigid connection, the ink jet head and the ink tanks must always be moved jointly. This is problematic, given the relatively large mass.
On the other hand, an ink jet head of stacked construction made of individual modules is known that operates by the edgeshooter principle. See German Patent DE 44 43 254 C1. The individual module comprises three plates located one above the other. When the modules are assembled to make an ink jet head, spacer parts are also inserted between adjacent modules. Nothing further is the about how the ink is supplied.
A module for an ink jet head has become known from German patent disclosure DE 44 43 245 A1 which comprises two switch modules and one ink jet printing module, disposed between them, operating on the edge shooter principle. The ink jet printing module is composed of a first cover plate, a middle plate, and a second cover plate, as well as piezoelectric actuators that are disposed on the cover plates. Ink jet printing chambers are formed into the cover plates, and jet openings with jet conduits are formed into the middle plate; all the jet openings are located in the same plane. Once again, the ink supply per se is still not addressed.
A configuration for an ink jet head in piezo-planar technology is also known--see German Utility Model DE 295 21 128 U1--in which plates are layered one above the other, and ink supply conduits, ink jet printing chambers, jet conduits and jet openings are formed into them. The ink supply conduits are supplied from a common supply conduit.
Finally, a pressure absorber for an ink jet printer is known as well in the prior art. See European patent disclosure EP 0 383 558 A1. The pressure absorber is inserted as a separate component group between an ink tank and an ink jet head and communicates with them via one ink hose each. In this way, the pressure absorber also acts as an ink supply unit. The pressure absorber has a pressure equalization diaphragm. The design and mode of connection allow only a one-piece ink jet head, which is embodied by the edge shooter principle.